Rheostat switch



June 25, 1940. H. w. BATCHELLER BHEOSTA'I' SWITCH Filed March 4, 1937 071mm l/3"";

Patented June 25, 1940 UNITED STATES PATENT OFFICE RHEOSTAT SWITCHApplication March 4,

3 Claims.

This invention relates to improvements in rheostat switches such as arecommonly employed in controlling heating units for automobiles.

It is an object of the present invention to provide a switch havingimproved structural features by which the switch can be more readilyassembled and taken apart with less liability of damaging one or more ofthe parts in the process. It is a further object of the invention toprovide a switch structure having greatly improved wearing qualities.

For a more complete understanding of the invention, reference may be hadto the disclosure of an embodiment thereof in the description whichfollows and on the drawing of which Figure 1 is an exploded perspectiveview of a switch mechanism embodying the invention.

Figure 2 is a longitudinal sectional view of the assembled switch.

Figure 3 is a front elevation of the operating knob and shield.

Figure 4 is a perspective view of the shield.

Figure 5 is a rear elevational view of the housing shell.

Figure 6 is a section on the line 66 of Figure 2.

Figure 7 is a front elevational view of the base member.

The switch structure is enclosed in a cupshaped housing shell Hi, theopen end of which is normally closed by a base member l2 which fits intoit. The base member is preferably of refractory material such asporcelain, molded to shape, and it may be provided with a peripheralshoulder l4 against which the lip or rim of the shell bears. In order tohold the base and shell together in assembled relation, a bail'lB isprovided, this bail being preferably made of resilient wire bent into aU shape. The ends of the bail are hooked as at IE! to enter a pair ofinclined slots 20 in opposite side walls of the shell in. These slotsslope away from the base, the re mote end of each slot having a notch 22therein. The rear face of the base member l2 may be provided with atransverse groove 24 of suitable size to receive the transverse portionof the bail Hi. In assembling the base member and the shell, the base I2is inserted in the shell [0 until the edge of the shell bears againstthe shoulder 14. The bail IE is then applied to the rear face of thebase member, the transverse portion of the bail entering the groove 24.The arms of the bail are swung around until the hooked ends l8 enter theslots 20. By pressing laterally against 1937, Serial No. 128,949

the arms of the bail, the hooks l8 ride along the inclined slot 20 untilthey snap into the notches 22. The camming effect of the inclined slotsis to put the bail under tension so that the shell is held firmlyagainst the base member. In order to provide suitable resilience in thebail, end portions 26 of the transverse part of the bail are reverselybent so as to stand away from the bottom or the groove 24. This providesspring portions which yield sufficiently to permit the hooks [8 to enterthe notches.

The inner or forward face of the base member l2 is provided with anarcuate groove or channel 3! within which is disposed a helical coil 32of resistance wire. The diameter of the coil is less than the width ofthe groove 30 but greater than its depth, so that the coil projectsslightly from the groove as indicated in Figure 2. At one end the groovehas a portion of extra depth. In this deeper end portion of the groovethe turns of the coil 32 are entirely within the groove. The groove isprovided with a series of lateral recesses 34. These recesses may be oneither or both sides of the groove. Prior to inserting the coil 32 intothe groove, a suitable amount of cementitious material is placed in thegroove. Then the coil is pressed into the cement so that the cementsurrounds the portion of the coil which is actually within the grooveand also fills the lateral recesses substantially flush with the face ofthe base member l2. These lateral recesses ensure the presence of asufficient amount of cement to make a good bond for the coil 32, thecoil being firmly embedded in the body of cement within the groove. Theportion of the coil in the deeper end portion of the groove is entirelycovered by cement, and the lead wire at this end of the coil iselectrically connected to a metal plate 36 which is secured to theforward face of the base member as indicated in Figures 1 and 7.

Within the arc of the groove 30 and concentric therewith is a centraldepression All in the base member 12. A metal strip 42 extends radiallyfrom the depression 40 on the forward face of the base It and isintegral with an eye 44 which projects into the recess 40. The element42 is secured to the base as at 15 by a threaded sleeve 48 whichprojects through the base and receives a screw 58 at its rear end toserve as a binding post. The plate 36 is likewise secured as at 52 by asimilar binding post.

The elements of the switch which cooperate with the elements carried bythe base member I 3 comprise a contact shoe which may consist of a pieceof sheet copper cut to suitable shape and provided with an offsetcontact element 62 adapted to slide across the member 42 and the plate36, and along the coil 32, and an offset contact element G4 at its otherend adapted to slide on the forward face of the eye 44. These contactelements 62 and 64 are preferably of substantial width so that theypresent as much wearing surface as possible for contact with theelements on which they slide. When the shoe G is in either of itsextreme positions, the contact element 62 is either resting on themember 42 or is hearing on the end portion of the coil 532 remote fromthe plate 35. In order to rotate the shoe, it is provided with a centralnon-circular aperture 66. In this orifice is fitted the end portion 68of the stem Ill. The stem is hollow, as indicated in Figure 2, andcontains a plunger 12 which is pressed forward by a spring 74. The stem70 passes through and fits in a non-circular aperture 18 in a fiber diskIS. The disk I6 has a lug 'I'l projecting from its periphery to engage atongue I9 struck up from the shell Ill to act as a stop, thusdetermining the extreme angular positions of the shoe 50 which rotateswith the F disk T6. The stem Ill is permanently secured in assembledrelation with the disk '56 by a pair of tongues 80 which are cut andcurled out from the sides of the stem by a suitable tool after the endportion of the stem has been inserted through the aperture 78. The stem73 is pref-- erably mounted loosely in the disk It so that the endportion 68, after being passed through the aperture 66 of the shoe 60,can center itself readily in the eye 44. As indicated in Figure 2, aspring 83 surrounds the end portion til of the stem between the disk 76and the shoe 6B. This serves to press the contact elements of the shoeconstantly against the respective switch elements on the base.

Assembled with the disk iii are a pair of nested tubular members 84 and86 which serve respectively as a lamp socket and shaft element, Thesocket 84 has a flange 88 at its rear end with notches 90 to receive apair of ears 92 at the rear end of the shaft element 86. The ears 9?!pass through the notches 9i) and through suitable apertures 94 in thedisk It. The ears are then bent against the rear face of the disk I6 tohold these parts permanentlyin assembled relation. The socket 84 isprovided with suitable bayonet slots 84 adapted to receive the usualpins 9t on the base 98 of a lamp bulb IBIS. The tip I02 of the lamp ispressed against the yielding plunger 12 when the lamp is inserted in thesocket.

For rotation of the disk 16 and the parts associated therewith, theshaft element 86 is keyed to another tubular shaft element I04 whichtelescopes thereon. The shaft m4 is notched as at I06 to receive a lugor key I Ila. This key is preferably formed by striking up from theshaft element 86 a pair of lugs on lines of bend which extend parallelto the axis of the shaft as indicated in Figures 1 and 6. Thesestruck-up lugs can be made of substantial length so as to provide astrong abutment to be engaged by the edges of the key slot I06. On theouter end of the shaft I04 is a cylindrical finger knob III), thecylindrical surface thereof being preferably knurled. This knob may bemade of plastic material and is preferably molded onto the outer end ofthe shaft member I04 so that it becomes a permanent unit therewith. Asindicated in Figure 1, the forward end of the shaft member [I14 is leftopen so that the rays of light from the lamp I00 can shine in an axialdirection. To tone down this illumination, a suitable shield IIZ oftranslucent material may be provided, this shield being of U shape andbeing wide enough to cover at least the open end of the shaft memberI04. The arms H4 of the U-shaped shield project rearwardly and areadapted to fit frictionally on a pair of forwardly projecting arms H6 ofa support member I20 which is keyed by a key I22 on a threaded sleeveI30, the latter being permanently attached to the shell I0 so as to forma part of the housing for the switch. As shown in Figure 3, the sideportions of the finger knob III] are exposed for access so that the knobcan readily be turned.

In order to provide a yielding detent so as to indicate to the operatorby the sense of touch the on and off positions of the switch and to holdthe switch yieldingly in such positions, the rear end I32 of the sleeveI30, which is spun against the inner face of the shell I0 so as tosecure the sleeve permanently to the shell, is dented as at I34 and I36in Figure 5. The flange 38 of the socket member 84 is pressed againstthe rear end I32 of the sleeve I30 by the spring 82. On this flange 38 asuitable lug or bulge I40 is formed, this bulge being adapted to rideinto and out of the notches I34 and I36 when the switch is in its offand on positions respectively.

Various modifications and changes may be made in the specificconstruction of the improved features of the switchherein described,without departing from the spirit or scope of the invention as definedin the following claims.

I claim:

1. In an electric switch, a stationary switch element, a movable switchelement, and rotatable means for moving said elements into and out ofcontact, said means including a tubular shaft having two telescopingparts, the inner part having a pair of adjacent lugs struck up from thewall thereof on lines of bend which are parallel to the axis of theshaft, the outer part having a notch therein the side edges of which areengaged by said lugs.

2. In a tell-tale electric switch, a housing including a sleeveprojecting therefrom, a switch within said housing, means for operatingsaid switch, said means including a tubular shaft element having itsinner end portion rotatably projecting into said sleeve and acylindrical knob on its outer end portion, a stationary shield extendingdiametrically across the end of said knob and covering the end of saidshaft, portions of the cylindrical surface of said knob being leftaccessible for manipulation, and means for sup porting said shield.

3. In a tell-tale electric switch, a housing including a sleeveprojecting therefrom, a switch within said housing, means for operatingsaid switch, said means including a tubular shaft element having itsinner end portion rotatably projecting into said sleeve and acylindrical knob on its outer end portion, a support elementnonrotatably mounted on said sleeve, said support element having a pairof parallel arms projecting forward above and below said knob, and ashield carried by said arms, said shield having a portion extendingdiametrically across the outer end of said knob and covering the outerend of said shaft but leaving the sides of the knob exposed to accessfor operation of the switch.

HUGH W. BATCHELLER.

